A9n

A9n is a simple tool to keep ruby/rails apps configuration maintanable and verifiable. It supports Rails 3.x, 4.x and Ruby 2.0. 2.1, 2.2, 2.3. Ruby 1.8 and Rails 2.x are not supported since version 0.1.2. Ruby 1.9 is not supported since version 0.4.0.

Why it's named a9n? It's a numeronym for application (where 9 stands for the number of letters between the first a and last n, similar to i18n or l10n).

Installation

Add this line to your application's Gemfile:

gem'a9n'

And then execute:

$ bundle

Add configuration.yml.example and/or configuration.yml file into the config
directory. When none fo these files exists, A9n::MissingConfigurationFile
exception is thrown.
If both file exist, content of configuration.yml is validated. It means that
all keys existing in example file must exist in local file - in case of missing
keys A9n::MissingConfigurationVariablesError is thrown with the explanation what is missing.

Set application root and load configuration by adding to your application.rb or environment.rb right
after budler requires:

A9n.root=File.expand_path('../..',__FILE__)A9n.load

This step is not required ,if you don't use a9n in the environment settings or initializers.
It works with Rails by default. If you want to use A9n with non-rails app
you may need to tell that to A9n by:

A9n.local_app=MyApp

Usage

You can access any variable defined in configuration files by delegating it to
A9n. E.g:

A9n.app_host# => `knapik.cc` in production and `localhost:3000` in developmentA9n.email_from# => `no-reply@knapik.cc` in both envs

Custom and multiple configuration files

If you want to split configuration, you can use multiple files. All files from config/a9n are loaded by default, but you may pass custom paths as an argument to A9n.load e.g. A9n.load('config/facebook.yml', 'config/mongoid.yml'). In such cases config items are accessible through the scope consistent with the file name.

E.g. if you have config/a9n/mandrill.yml:

defaults:username:"joe"api_key:"1234asdf"

You can access it by:

A9n.mandrill.username# => `joe`A9n.mandrill.api_key# => `1234asdf`

Mapping ENV variables

Sometimes, you don't want to store a single secret value in the repo and you prefer having it in ENV variable. You can easily map it using :env symbol as a value:

production:access_token::env

Capistrano

If you use capistrano and you feel safe enough to keep all your instance ( staging, production) configuration in the repository, you may find it useful to use capistrano extensions.
Just add an instance configuration file e.g. configuration.yml.staging, configuration.yml.production (NOTE: file extension must be consistent with the capistrano stage) and add

require'a9n/capistrano'

to your Capfile. This way configuration.yml.<stage> overrides configuration.yml on each deploy.